Bioindicators Of Water Quality Research Articles

Variations of zooplankton community as bioindicators of eutrophication and water quality in shallow Yangtze Lakes

Variations of zooplankton community as bioindicators of eutrophication and water quality in shallow Yangtze Lakes

The Role of Rotifera as Sentinel Organism of Trophic Structure on Freshwater Ecosystems

For determining the trophic condition of freshwater ecosystems, rotifera, a phylum of tiny and near-microscopic pseudocoelomate creatures, are important sentinel or bioindicator species. For ecological monitoring and water quality evaluation, they are perfect because of their species composition, variety, and abundance, which react quickly and sensitively to changes in environmental quality and nutrient availability. Aquatic environments consist of both biotic and abiotic interactions. There is a relationship between these things. They create an ecosystem's cumulative environmental condition, which can be classified as oligotrophic, mesotrophic, or eutrophic at present. Of all the diverse types of plants and animals that live in water, zooplankton are crucial for controlling the systematic processes that keep the environment healthy. Rotifers are one of the planktonic groups of zooplanktons that perform very well in controlling the ecosystem as a whole. These large organisms are also occasionally seen as an avoidable instrument for determining the state of the environment. It is always appropriate to use these creatures as bio-indicators of the ecosystem's trophic structure and pollution level. A good bio-indicator of water quality might be the group of rotifers or a single species, depending on the many indexes and the link between various biological, chemical, and physical features such as the dynamics and diversity of the described organism. Rotifers react strongly to eutrophication, or nutrient enrichment, especially when it comes to the availability of phosphate and nitrogen.

Assessment of Bacterial Community and Other Microorganism Along the Lam Takhong Watercourse, Nakhon Ratchasima, Thailand.

Lam Takhong, a vital watercourse in Nakhon Ratchasima province, Thailand, supports agricultural, recreational, and urban activities. Originating in a national park, it flows through urban areas before discharging into a dam and running off via the sluice gate. While water quality monitoring is routine, microbial community data have never been reported. This study assesses the microorganism diversity and functional genes in Lam Takhong watercourse using a shotgun sequencing metagenomics approach. Water samples were collected from the upstream, midstream, and downstream sections. The midstream area exhibited the highest abundance of fecal coliform bacteria, plankton, and benthos, suggesting elevated pollution levels. Genes related to metabolism, particularly carbohydrate and amino acid pathways, were predominant. Proteobacteria was the most abundant phylum found in the water, with Limnohabitans as the dominant planktonic bacteria. Bacteria such as Staphylococcus, Mycobacterium, Escherichia, Pseudomonas, Enterococcus, Neisseria, Streptomyces, and Salmonella were detected, along with antibiotic resistance genes, raising public health concerns. These findings emphasize the need for microbial monitoring in the Lam Takhong to determine the potential water quality bioindicator and prevent potential disease spread through the water system.

Monitoring water contamination through shellfish: A systematic review of biomarkers, species selection, and host response.

Monitoring water contamination through shellfish: A systematic review of biomarkers, species selection, and host response.

Gastropods as Bioindicators of Water Quality in Telindale Beach, Rote Tengah District, Rote Ndao Regency

Telindale Beach is part of the Central Rote Sub-district in the Rote Ndao Regency. The beach is also a seaside region with many community activities, including tourism, recreation, and sales. These activities have a significant impact on the health of aquatic ecosystems. The presence of pollutants in water might cause a decline in its quality. Gastropods are among the species that are sensitive to changes in water quality. This study sought to provide information on gastropod diversity as a bioindicator of water quality at Telindale Beach. This study was both descriptive and quantitative, with the location determined through purposive sampling. The line-transect approach was applied at three locations, each with a different substrate. The data were evaluated using diversity, uniformity, and dominance index techniques. The research revealed that the gastropods identified at the beach belonged to 13 families, 15 genera, and 19 species, with 112 individuals across all stations. The diversity index ranged from 0.27 to 2.33 (moderately contaminated), the uniformity index was 0.84-0.91 (high), and the dominance index was 0.12-0.31 (moderate). According to the species diversity index data, the waters near Telindale Beach were the most polluted. Keywords: bioindicator, gastropods, Telindale Beach

Aquatic Biofilm as Water Quality Bioindicator in the Upstream Part of Cisadane River

Abstract Changes in river water conditions from anthropogenic activities can be indicated by microbiota such as periphytons and bacteria. This study assessed water quality in the upstream Cisadane River at three sampling sites in Ranca Bungur, Lido, Bogor, focusing on periphyton and bacteria as bioindicators at two different time periods. Data analysis included community structure, the assemblge pattern, and pollution level determination from current (2024) and previous research (2007). Periphytic diatoms dominated across stations and periods, with different composition of genera in the whole periphyton community; while bacteria were primarily from the Aeromonas group. The change of anthropogenic activities tend to change the diversity and the density of organisms assemblaged in the aquatic biofilm. The presence of these microbiota in biofilms suggests moderate organic pollution in the upstream Cisadane River, strongly correlated with nitrate and orthophosphate levels. Nevertheless, it is important to note that the pollution levels in recent studies occur further upstream.

Plankton Community Structure as a Bioindicator of Sustainable Water Quality in Koi (Cyprinus carpio) Ponds

Plankton Community Structure as a Bioindicator of Sustainable Water Quality in Koi (Cyprinus carpio) Ponds

Distribution and dynamics for the ecological assessment of Asan Wetland through periphyton -a water quality indicator

The Asan Wetland is an important freshwater wetland in Uttarakhand’s Dehradun district. It is known for its diverse flora and fauna and as a stopover for migratory birds. Periphyton, an essential biological component of aquatic ecosystems, serves as a bioindicator of water quality and ecosystem integrity. This study fills a gap in our knowledge of the Asan Wetland’s ecological health by analyzing periphyton populations and a number of physicochemical characteristics across three selected sites from November 2021 to October 2023. Selected sites named as Site 1(S1), Site 2(S2), Site 3 (S3). Monthly variations in parameters such as water temperature, pH, turbidity, transparency, total dissolved solids (TDS), electrical conductivity, dissolved oxygen (DO), total hardness, alkalinity, biological oxygen demand (BOD), chemical oxygen demand (COD), and nutrients were collected, identified and assessed using Ms-excel and Past software. Phosphorus levels in the Asan Wetland indicated a moderate to high nutrient load, peaking in August (1.20–1.25 mg/L) across all three sites and dropping to their lowest in January (0.35–0.65 mg/L). Nitrate levels were moderate, with the highest concentrations in December (1.40–1.55 mg/L) and the lowest in July (0.25–0.35 mg/L), showing similar seasonal patterns across sites. The periphyton was represented in this study by 18 different periphytic taxa that belong to three different classes. These classes include Bacillariophyceae (Cymbella, Navicula, Nitzschia, Fragilaria Meridion, Synedra, Gomphonema, Tabellaria, and Diatoma), members of the Chlorophyceae Ulothrix, Spirogyra, Cosmarium, Microspora, Chlorella, Oedogomium, Zygnema, and Cladophora are, while Phormidium is a member of the Cyanophyceae. The peak periphytic density (individuals/cm2) recorded was 322.67 ± 89.08 × 103 in January, with all three classes exhibiting maximum values at S3, the minimum periphytic density (individuals/cm2) recorded was 18 ± 5.57 × 10³ in August. The annual percentage composition of periphytic flora in the Asan wetland over 2 years indicates that Bacillariophyceae constituted the predominant group (89%–90%), succeeded by Chlorophyceae (7%–9%) and Cyanophyceae or Myxophyceae (1%–4%) across three sites. The canonical correspondence analysis (CCA) of periphyton among different sites during both years of the study suggested that S3 was more diverse, followed by S1 and S2, represented 64.93%, 35.07% of the variance with eigenvalues of 0.01794, 0.00968 respectively. PCA suggested that PC1 and PC2 were represented by 93.98% and 6.015% of the variance with eigenvalues 279.149 and 17.8675, respectively The multivariate cluster analysis showed the similarity of periphyton at three different sites during the 2-year study. The findings of this study emphasize the need for targeted management strategies to maintain the ecological health of the Asan Wetland.

Evaluation of the cytome (micronuclei and nuclear anomalies) in Lithobates spectabilis from two ponds in La Caridad Cuaxonacayo, Ixtacuixtla

The increase in industrial and agricultural activities in Mexico has led to higher environmental pollution, affecting surface water quality and, consequently, biodiversity. Jagüeyes, water bodies formed by runoff, are particularly vulnerable to pollutants, with their concentration depending on surrounding land uses such as agriculture and pesticide application. Pesticide pollution negatively impacts local biodiversity by harming aquatic organisms. Jagüeyes serve as refuges for various species, some of which can act as bioindicators of water quality. One example is Lithobates spectabilis, whose aquatic-terrestrial life cycle and permeable skin make it suitable for evaluating the effects of pollution. This study analyzed genotoxic damage in L. spectabilis using biomarkers such as micronuclei (MN) and erythrocytic abnormalities (EA) in two jagüeyes in Cuaxonacayo. Three adult specimens were collected, and their blood samples were analyzed for abnormalities. The results showed an MN frequency of 0 in the control group, 0.7% in zone A, and 0.33% in zone B. Although there were significant differences between the contaminated zones and the control (p<0.001), no differences were observed between zones A and B. The results indicate that the jagüeyes in Cuaxonacayo have pollution levels affecting the genetic integrity of L. spectabilis, which could impact local biodiversity in the long term. Further research on the xenobiotics present in the water is recommended. The increase in industrial and agricultural activities in Mexico has led to higher environmental pollution, affecting surface water quality and, consequently, biodiversity. Jagüeyes, water bodies formed by runoff, are particularly vulnerable to pollutants, with their concentration depending on surrounding land uses such as agriculture and pesticide application. Pesticide pollution negatively impacts local biodiversity by harming aquatic organisms. Jagüeyes serve as refuges for various species, some of which can act as bioindicators of water quality. One example is Lithobates spectabilis, whose aquatic-terrestrial life cycle and permeable skin make it suitable for evaluating the effects of pollution. This study analyzed genotoxic damage in L. spectabilis using biomarkers such as micronuclei (MN) and erythrocytic abnormalities (EA) in two jagüeyes in Cuaxonacayo. Three adult specimens were collected, and their blood samples were analyzed for abnormalities. The results showed an MN frequency of 0 in the control group, 0.7% in zone A, and 0.33% in zone B. Although there were significant differences between the contaminated zones and the control (p<0.001), no differences were observed between zones A and B. The results indicate that the jagüeyes in Cuaxonacayo have pollution levels affecting the genetic integrity of L. spectabilis, which could impact local biodiversity in the long term. Further research on the xenobiotics present in the water is recommended.

Density of Green Mussels (Perna viridis) and Its Impact on Growth and Lead Accumulation in Polyculture Systems in Tropical Waters

Aims: Green mussels (Perna viridis) are filter-feeding organisms known for accumulating heavy metals, including lead (Pb), in their tissues, making them valuable bioindicators of water quality. Study Design: This study aimed to assess the impact of different stocking densities on the growth and lead accumulation in Perna viridis. Place and Duration of study: This study was conducted at a traditional pond in Ujungpangkah Subdistrict, Gresik, East Java, over a period of 21 days, from June 27 to July 18, 2024. Methodology: A Completely Randomized Design (CRD) was employed with three treatment groups: Treatment A (10 mussels/m²), Treatment B (20 mussels/m²), and Treatment C (30 mussels/m²). The parameters measured included the absolute flesh width, daily growth rate, and lead content in the mussels. Result: Statistical analysis using Analysis of Variance (ANOVA) revealed no significant differences in the daily growth rate among the treatments (p > 0.05), suggesting that stocking density did not significantly influence growth. However, significant differences in the absolute flesh width were observed, with Treatment C showing the largest absolute flesh width at higher density. Additionally, lead accumulation increased with stocking density, with mussels in Treatment C accumulating the highest levels of lead (1.14 mg/L). This suggests that, while the growth rate was unaffected by density, the absolute flesh width are influenced by stocking density. The bioaccumulation of lead in mussels was also interpreted descriptively, considering the mussels' need for a suitable environment to mitigate environmental stressors. The findings underline the importance of considering both the growth and environmental health of the mussels, especially in relation to density management to prevent heavy metal accumulation.

An Empirical Analysis on the Breeding and Feeding Behaviour of Estuarine Rice Fish Oryzias melastigma (McClelland, 1839)

The breeding and growth characteristics of Oryzias melastigma were investigated under controlled laboratory conditions to assess its suitability for aquaculture. The species exhibited a short-generation time of 2 to 3 months that thriving in artificial-seawater at 28°C with a 14-hour light/10-hour dark-cycle. Sexual-dimorphism became apparent after one-month; with males developing a prominent anal-fin, aiding sex identification for experimental-populations. Feeding-experiments revealed that Oryzias melastigma, preferentially consumed early instar mosquito-larvae, showing high feeding-efficiency, particularly on smaller-prey. Additionally, the species demonstrated increased reproductive-success when supplemented with Ulothrix, suggesting its effectiveness as a feed to enhance egg-production and hatchling-survival. The sensitivity of eggs and larvae to pollutants like ammonia and CO2 indicates the species' potential as a bio-indicator for water-quality. Statistical analysis of reproductive-output indicated that a mature-female, could produce over 1.5 million eggs annually; contributing to aquaculture-systems as a food-source for carnivorous-species. This potential-biomass, when applied to fish farming, could significantly enhance the production of species like Lates calcarifer. The study highlights breeding and feeding behaviour of estuarine rice fish, Oryzias melastigma.

Macroinvertebrados bentónicos como bioindicadores para evaluar la calidad del agua en el río Cañipia, Cusco, Perú

Introduction. Benthic macroinvertebrates (BMIs) are widely used as bioindicators of water quality due to their sensitivity to physicochemical alterations caused by pollution. Their presence and community composition provide a comprehensive assessment of the ecological status of aquatic ecosystems. Objective. This study aimed to assess the water quality of the Cañipia River, located in Cusco, Peru, using three biotic indices: BMWP/Col, ABI, and EPT. Materials and Methods. Sampling was conducted at four stations during the dry and wet seasons. BMIs were identified at the family level to calculate diversity and biotic indices. Additionally, physicochemical parameters were analyzed, and heavy metal concentrations in water and sediments were determined. Results. The families Elmidae and Chironomidae were the most abundant. According to the BMWP/Col index, water quality ranged from critical to doubtful, while the ABI index indicated a poor to good status. The EPT index classified water quality as poor to moderate. Simpson’s index revealed fluctuating diversity, ranging from low to high during the dry season and from moderate to high during the wet season, whereas Shannon’s index indicated low to moderate diversity. Margalef’s index (DMg) was higher in the wet season. Regarding metal contamination, only station RCañi1, located upstream of the formal mining area, exceeded Peruvian regulatory limits for Ba, Cu, Mn, and Zn in water. Canonical Correspondence Analysis (CCA) showed seasonal relationships between metal concentrations and biotic indices. Conclusions. The three biotic indices suggest a moderate impact on the water quality of the Cañipia River, likely influenced by anthropogenic factor

Macroinvertebrates as bioindicators of water quality in the Skawa River and Mucharskie Lake (Southern Poland)

Aquatic macroinvertebrates are organisms’ sensitive to changes in the environment in which they function and are therefore used to assess the quality of surface waters. This study aimed to assess the water quality of the Skawa River and Mucharskie Lake based on benthic macroinvertebrates, using the BMWP-PL index. Water samples from six research sites were utilised for the study – three on the Skawa River and three on Mucharskie Lake. Various macroinvertebrates were identified in water samples from the study sites, such as mayflies, caddisflies, stoneflies, beetles, crustaceans, snails, and leeches. The assessment of the water quality of the Skawa River and Mucharskie Lake, taking into account the BMWP-PL index, indicates a generally poor condition of the studied waters. The BMWP-PL indices obtained at the studied sites ranged from 3 to 93 points. Such a score corresponds to four water quality classes – II, III, IV, and V. Points S1, S2 and S6 on the Skawa River were characterized by good and moderate water quality (II and III class). On the other hand, bad water quality was characterized by sites S3 (Dabrówka) and S4 (Mucharz) on Mucharskie Lake.

IDENTIFICATION OF HEAVY METAL Cu AND Zn IN THE MEAT OF NILE TILAPIA (Oreochromis niloticus) AT IPAL BOJONGSOANG, BANDUNG REGENCY, WEST JAVA

The Bojongsoang Wastewater Treatment Plant (IPAL) in Bojongsoang District, Bandung Regency, West Java, is a facility that processes wastewater from the city of Bandung. In the IPAL pond, there are Nile tilapia that live there and can serve as bioindicators of water quality. However, these fish are utilized by the surrounding community through fishing and netting for consumption and sale. This study aims to determine the safety level of Nile tilapia (Oreochromis niloticus) meat in the Bojongsoang IPAL based on the content of heavy metals Cu and Zn. The research was conducted from May to October 2024. The method used is a survey method with purposive sampling technique conducted at four pond sample collection locations. The accumulated heavy metal content in the Nile tilapia meat from the Bojongsoang IPAL Treatment Pond is as follows: Cu (0.1649 mg/kg, 0.1199 mg/kg, 0.1896 mg/kg, 0.1825 mg/kg) and Zn (2.5308 mg/kg, 1.9651 mg/kg, 2.3628 mg/kg, 2.5125 mg/kg). The levels of these heavy metals are still below the maximum limits set by Ditjen POM RI in 1989, indicating that the Nile tilapia meat collected from the Bojongsoang IPAL Treatment Pond is still safe for consumption based on its Cu and Zn heavy metal content.

Spatial-Temporal Variations of Zooplankton in Relation to Selected Limnological Parameters: A Case of Kisii Town Wastewater Treatment Plant, Kisii County, Kenya

Zooplankton have been used as bioindicators of water quality. In this study, we assessed the spatial-temporal variations of zooplankton in the Kisii town wastewater treatment plant and how they were influenced by limnological parameters between May and August 2021. Triplicate zooplankton samples were collected monthly for laboratory analysis. Physical parameters were measured in situ using a YSI multi-parameter probe while triplicate wastewater samples were collected for chemical parameters analyses ex situ. Eleven (11) zooplankton species were identified belonging to three groups. Cladocera was represented by 5 species (45.5 %), Rotifera by 4 species (36.4 %), and Copepoda by 2 species (18.2 %). The total zooplankton density recorded was 515IndL-1 with the family Cladocera dominating (57.7 %) followed by Copepoda (22.8 %) then Rotifera (19.5 %) with the least number in the population density. The limnological parameters measurements indicate considerable wastewater pollutant removal during polishing but negatively influenced zooplankton diversity. Therefore, zooplankton can be used to monitor wastewater treatment progress.

Macrozoobenthos community structure as a bioindicator of water quality in the Banjaran River, Banyumas

The Banjaran River is one of the rivers in the Banyumas Regency. This research aims to produce information related to macrozoobenthic community structure as a bioindicator of water quality in the Banjaran River and to produce information related to water quality in the Banjaran River for macrozoobenthic life. The research was conducted in September 2022 – February 2023 on the Banjaran River, Banyumas. This research uses a survey method, sampling was carried out 3 times in September-November 2022. The sampling method was purposive random sampling, namely the river was divided into 3 stations based on certain criteria. The results of this research obtained 15 species and were divided into 11 families, namely Perlidae, Psychomyiidae, Thiaridae, Lumbricidae, Naididae, Gecarcinucidae, Palaemonidae, Elmidae, Hydropsychidae, Atyidae, and Chironomidae in the Banjaran River. The highest abundance of individuals was at station two, namely 3156 individuals/m2. The dominant species is Melanoides tuberculata with an abundance of 1852 individuals/m2 at station two. The dominance index values at the three stations ranged from 0.1864 to 0.2886, which is relatively low. The water quality in the Banjaran River for macrozoobenthic life is still quite good based on the results of measuring environmental parameters which consist of physical parameters, namely water temperature and current speed.Keywords: Banjaran River, Macrozoobenthos Community, Water Quality Indicators

Diversity and Ecology of Aquatic Insects

This paper presents current information on the variety, ecological characteristics, and preservation of aquatic insects. Although aquatic insects play vital roles in aquatic food webs, nutrient cycling, and serve as bioindicators of water quality, their numbers are currently under risk due to several human-induced stressors, such as habitat destruction, pollution, the introduction of exotic species, and the effects of climate change. This page provides an overview of the primary classifications of aquatic insects, their life cycles, their ability to adapt to aquatic environments, and their ecological roles. This analysis focuses on the conservation obstacles that aquatic insects encounter, such as the consequences of changes in land utilization, chemical pollutants, modifications to water flow patterns, and increasing water temperatures. There are still important areas of information that need to be filled in when it comes to understanding the classification and ecological behavior of aquatic insects in various regions. In addition, we need to better understand the various factors that are negatively affecting their populations, as well as develop efficient methods for conserving them. . KEYWORDS :Bioindicators, Metamorphosis, Diapause, Benthos, Trophic level

FISH ABUNDANCE AND DIVERSITY AS BIOINDICATOR OF WATER QUALITY IN SENGGURUH AND KARANGKATES RESERVOIR

Reservoirs serve as beneficial recreation areas for the surrounding community. Reservoirs are also habitats for various types of flora and fauna. Severalfamous reservoirs in East Java due to their fisheries potential are Sengguruh and Karangkates Reservoirs. This study aimed to determine the abundance and diversity of fish as bioindicators of water quality in Sengguruh and Karangkates Reservoirs. Fish and water quality parameters weresampled at three points in each reservoir, namely residential, tourism, and fisheries areas. All data were analyzed descriptively, while the correlations between fish abundance and diversity with water quality were determined using the Pearson’s correlation test. According to the results, three fishfamilies were found in Sengguruh Reservoir with a relative abundance of 26 - 55 ind/200 m and a diversity index ranging from 1.6510 to 1.7239. Meanwhile, in Karangkates Reservoir, four fishfamilies were found with a relative abundance of 41-43 ind/m and a diversity index of 1.7806 - 1.8787. The water quality parameters showed temperature of26-28.7℃, pH of 7.5-8.5, DO of 4.5-8.2 mg/L, CODof 20-28 mg/L, ammonia of 0.18-0.77 mg/L, and nitrate of 6.7 - 21 mg/L. Based on the diversity index value, both reservoirs are classified as lightly polluted, with abundance variables have no correlation with temperature, yet negative correlation is presented with DO, pH, and nitrate. In contrast, a positive correlation is shown with phosphate and ammonia.

Eukaryotic Microalgae Communities from Tropical Karstic Freshwater Lagoons in an Anthropic Disturbance Gradient Microscopic and Metagenomic Analysis.

The Yucatan aquifer sustains the people living in the Mayan forest and its associated fauna. Human activities threaten water quality and the environmental services associated with it. To assess the eukaryotic microalgae community structure as a bioindicator of water quality, we employed a combined approach of microscopic and shotgun metagenomics to identify specific genera associated with shifts in physicochemical parameters in three permanent lagoons located in Campeche, Mexico. We could identify highly complex and diverse communities independent of human activity intensity, harboring an average of 362 genera at each lagoon. Of those, 85 were affected by alkalinity, carbonates, water hardness, and cyanuric acid levels. Some genera, like Nannochloropsis and Thraustotheca, showed significant negative correlations with lead concentration. The functional annotation of genes revealed these communities' highly diverse metabolic capabilities and the pending work for extensive genomic characterization of rare clades.

Unveiling the potential of parasites as proxy bioindicators for water quality assessment in river Jhelum Kashmir, India.

This study aimed to evaluate the effects of deteriorated physicochemical conditions in the river Jhelum on parasitic infestations and to investigate the potential of fish parasites as bioindicators of water quality. All the physicochemical parameters exhibited statistically significant differences based on both site and season (p < 0.01).The interaction term (Site × Season) was also kept in the model since it was statistically significant (p < 0.01). A parasitological survey of 360 schizothoracine fish revealed a 30.3% prevalence (109/360) of endohelminth infection. The study identified four predominant parasitic taxa across two distinct classes: Cestoda, including Adenoscolex oreini and Schyzocotyle acheilognathi, and Acanthocephala, comprising Pomphorhynchus kashmirensis and Neoechinorhynchus manasbalensis. For the assessment of parasitic load, we calculated the prevalence, mean intensity, mean abundance, and index ofinfection for each sampling period. Correspondence analysis identified associations between parasite occurrence and specific water quality parameters. Regression analysis, including R2 and p values, demonstrated a positive correlation between the number of parasites and both the proportion of infected fish and the ratio of infected to examined fish. Given that parasitic load is significantly influenced by a range of water quality parameters, fish parasites can serve as a robust indicator of declining water quality. Fish parasites are highly sensitive to water quality changes such as pollutants, toxins, and fluctuations in pH, temperature, and oxygen levels. Deteriorating water quality can stress fish, compromising their immune systems and increasing their susceptibility to parasitic infections. Additionally, complex life cycles of parasites can be disrupted by poor water conditions, making them indicators of water quality issues.